EP2595247B1

EP2595247B1 - Connector plug and method of fitting the connector plug to a coaxial cable

Info

Publication number: EP2595247B1
Application number: EP12193027.5A
Authority: EP
Inventors: Alexander Drewnicki; John Drewnicki; Richard Drewnicki
Original assignee: Commtel Innovate Ltd
Current assignee: Commtel Innovate Ltd
Priority date: 2011-11-17
Filing date: 2012-11-16
Publication date: 2019-05-22
Anticipated expiration: 2032-11-16
Also published as: EP2595247A3; GB2496653A; GB201119905D0; EP2595247A2

Description

The present invention relates to a connector plug for a coaxial cable, for example an RF television aerial cable or a satellite feed cable.
A coaxial cable typically comprises a solid copper inner conductor element, a braided copper outer conductor shield, a dielectric insulator sleeve between the inner and outer conductors, and an outer insulator sleeve. A standard connector plug for a coaxial cable typically comprises a body member having an outer connector element for electrical connection to the outer conductor, an inner element configured to receive the inner conductor element, a claw for gripping the outer insulator sleeve and a retaining cap that can be screwed onto the body member causing the claw to grip the sleeve. The claw also establishes an electrical connection between the outer conductor and the body member, by contact with a portion of the braided outer conductor after it has been folded backwards over the claw and the insulator sleeve.
Various types of coaxial connector plug are in common usage. One of these is the Belling-Lee or IEC 169-2 connector (also commonly referred to as a TV aerial plug), which typically has a push fit into a complementary socket and a central pin into which the solid core of the coaxial cable is inserted. Another is the F connector, which usually has screw-fit connection with a complementary socket and does not have a central pin, the solid core of the central conductor instead serving as the pin of the male connector.
WO 03/009423 A1 describes a connector for coupling to a multi-conductor cable having a center conductor and an outer conductor. The connector comprises a housing that is electrically connected to the outer conductor and an electrically conductive pin that is electrically connected to the inner conductor. WO01/13470 describes an electrical connector for coupling to an insulated electrical conductor. The electrical connector comprises a housing having an electrically conductive portion and a bore therein. US6796829B1 describes an electrical connector for coupling to an insulated single conductor electrical cable or coaxial cable. The connector has a housing having an electrically conductive portion and a bore therein. US5491315 describes a switching device for electrically activating and deactivating a coaxial cable junction between a coaxial cable terminus and a connection jack. The switching device comprises an electrically conductive housing having a first end adapted to be physically connected to the external terminus and a second end adapted to be physically connected to the connection jack. US 6080015 A describes a connector for coaxial cable having an inner conductor and an outer conductor separated by a dielectric. WO92/16983 describes a method of preparing a cable, a coaxial cable spacer and a plurality of coaxial cables. DE 29720827 U1 describes a coaxial connector for connecting a coaxial cable to an inner conductor and an outer conductor. The coaxial connector comprising a first and second contact means together with first and second clamping means.
In both cases, attaching the plug to the end of a coaxial is a time-consuming and fiddly process which involves carefully stripping off the outer insulator sleeve from the cable, folding back the braided outer conductor, removing part of the dielectric sleeve to expose the inner conductor, sliding a spacer (and for a Belling-Lee connector a hollow metal pin) over the inner conductor, sliding on the metal body member, trimming off the ends of the braided conductor, screwing on the retaining cap and finally trimming off any excess length of the inner conductor. Preferably, with a Belling-Lee connector, the inner conductor is also soldered to the pin. Completing this process correctly requires care and attention. If it is not carried out correctly, a poor electrical connection may result leading to loss of signal. Also, the plug is not securely attached to the cable and may come loose with use.
It is an object of the present invention to provide a connector plug for a coaxial cable that mitigates at least some of the aforesaid disadvantages.
According to an embodiment of the present invention there is provided a connector plug as defined in claim 1.
The provision of a piercing element that pierces the outer insulator sleeve and establishes an electrical connection between the body member and the outer conductor ensures a good electrical connection and therefore good signal transmission. The piercing element also ensures a very strong mechanical connection between the plug and the cable. Fitting of the plug to the cable is also greatly simplified and much quicker as compared to fitting a traditional coaxial plug.
The gripping element comprises a claw having a plurality of radially adjustable legs, at least one of the legs including a piercing element. The retaining cap is configured to adjust the radial positions of the legs.
The retaining cap is adjustable between first and second axially displaced positions, wherein when the retaining cap is in the first position the gripping element is disposed in the non-gripping configuration, and when the retaining cap is in the second position the gripping element is disposed in the gripping configuration. The gripping element can thus be adjusted to the gripping configuration simply by adjusting the cap.
The connector plug includes a spacer element that is removably attached to the body member, said spacer element being configured such that when attached to the body member it prevents movement of the retaining cap from said first position to said second position. This prevents the cap from being tightened too early (before the cable has been inserted).
According to one arrangement, the support element includes a connector pin that is configured to receive and support the inner conductor. In this embodiment the plug may be used as a replacement for a standard Belling-Lee connector. The connector pin preferably includes a resilient connector element that establishes an electrical connection with the inner conductor.
According to another arrangement, the support element is configured to support the inner conductor so that it serves as a connector pin. In this embodiment the plug may be used as a replacement for a standard F connector.
The body member may include a front part and a rear part that are connected together for relative rotation. Advantageously, the front and rear parts of the body member include complementary locking formations that may be engaged to prevent relative rotation. This makes it easier to tighten the retaining cap. Preferably, the complementary locking formations may be disengaged by relative axial movement of the front and rear parts of the body member to allow relative rotation. This allows the plug to be connected to a threaded socket without twisting the cable.
According to another embodiment of the invention there is provided a plug kit as defined in claim 8. The tool makes it very easy to trim away the outer insulating sleeve, the braided outer conductor and the inner dielectric insulator in a single operation, leaving an exposed length of the central conductor.
The cutter element is preferably resiliently biased to the non-cutting position.
According to yet another embodiment of the invention there is provided a method according to claim 10. The fitting method is extremely quick and simple as compared to the process for fitting a standard coaxial plug. The connected plug also has a much better electric and mechanical connections with the coaxial cable, making it more durable and reliable.
Embodiments of the invention will now be described by way of example with reference to the accompanying drawings in which:

Figures 1a-1c are isometric views of a connector plug according to a first embodiment of the invention, in which the plug is shown respectively in fully assembled, partly disassembled and fully disassembled configurations;
Figures 2a-2d are side sectional views of the first connector plug and a coaxial cable, illustrating the steps of a process for attaching the plug to the cable;
Figures 3a-3c are isometric views of a connector according to a second embodiment of the invention, in which the plug is shown respectively in fully assembled, partially disassembled and fully disassembled configuration;
Figures 4a-4d are side sectional views of the second connector plug and a coaxial cable, illustrating the steps of a process for attaching the plug to the cable, and Figures 4e-4h are external side views of the plug and the cable during the same steps;
Figure 5 is an isometric view of a cable trimming tool for use when attaching the plug to a coaxial cable, and
Figures 6a-6e are isometric views of the cable trimming tool, showing the steps of a process for trimming a coaxial cable.

The first plug 2 as illustrated in Figures 1a-1c and 2a-2d is compatible with a connector of the Belling-Lee type. The plug comprises a body member 4, a support element 6, a conductor pin 8 that is supported by the support element 6, a claw 10, a retaining cap 12 and a removable spacer clip 14. The body member 4 comprises a hollow, generally cylindrical element having a connector portion 16 at one end for connection to a coaxial socket and an externally threaded rear portion 18 at the opposite end. The body member 4 also includes an external knurled sleeve 19 that extends radially outwards beyond the rear portion 18. Internally, the body member 4 has a large diameter bore 20 towards the rear end 18 and a smaller diameter bore 22 at its front end 16, providing a step 24 at the junction of the two bores.
The support element 6 comprises a generally cylindrical sleeve that is made of an electrically insulating material and has a diameter slightly smaller than the diameter of the larger bore 20, so that when assembled the support element 6 sits closely within the bore 20 abutting the step 24. The support element 6 supports the hollow metal pin 8, which extends forwards towards the front end of the body member 4. The pin 8 includes an inwards facing tab 26 to establish an electrical connection with the inner conductor of a coaxial cable.
The claw 10 includes an annular disc 28 and four legs 30 that extend rearwards from the disc 28 approximately parallel to the longitudinal axis of the plug. Each of these legs 30 carries an inwards facing spur 32. The claw 10 is dimensioned to sit in the rear part of the large diameter bore 20 with the legs 30 protruding rearwards from the body member 4.
The retaining cap 12 comprises a hollow cylindrical sleeve having an internal screw thread that mates with the external thread on the rear part 18 of the body member 4. At the rear end of the cap a frusto-conical portion 34 provides an inwards inclined internal wall 36. This inclined wall 36 is configured to engage the ends of the legs 30 and to drive those legs inwards as the cap 12 is screwed onto the body member 4. The rear end of the cap includes an opening 38 to allow the insertion of a coaxial cable 40.
The spacer clip 14 is C-shaped and dimensioned to sit on the rear part 18 of the body member 4 between the knurled sleeve 19 and the threaded retaining cap 12. The clip 14 is made of a resilient material, for example a plastic material, allowing it to be easily removed from or replaced on the body member 4. When the spacer clip 14 is attached to the body member 4 it prevents the retaining cap 12 from being screwed completely onto the body member 4 and thus prevents the retaining cap 12 from driving the legs 30 of the claw 10 inwards. Tabs 42 on the ends of the C-shaped clip 14 allow it to be easily removed from the body member 4, after which tightening of the retaining cap 12 can be completed.
A process for attaching the plug 2 to a coaxial cable 40 will now be described with reference to Figures 2a-2d.
In Figure 2a the plug 2 is shown fully assembled and in a condition for receiving the prepared end of a coaxial cable 40. It should be noted that the spacer clip 14 is attached to the body member 4, thus maintaining a gap between the body member 4 and the retaining cap 12 and preventing the legs 30 of the claw 10 from being driven inwards.
The prepared end of the coaxial cable 40 is shown in Figure 2b. An end portion of the inner conductor 44 has been exposed by stripping away part of the outer insulator sleeve 46, the braided outer conductor shield 48 and the insulating dielectric sleeve 50. A tool for preparing the cable end as described is shown in Figure 5 and is described below.
In Figure 2c the prepared end of the coaxial cable 40 has been inserted fully into the plug 2, so that the cut ends of the outer insulating sleeve 46, the braided conductor shield 48 and the dielectric sleeve 50 abut the annular disc 28 of the claw 10. The solid central conductor 44 has been inserted into the hollow pin 8 where it is engaged by the resilient tab 26, thereby establishing an electrical connection between the conductor 44 and the pin 8. The spacer clip 14 has been removed to allow the cap 12 to be tightened.
Figure 2d illustrates the final stage of the attachment process, in which the retaining cap 12 has been tightened onto the body member 4. As the cap 12 is tightened the inclined walls 36 of the frusto-conical portion 34 push the legs 30 of the claw 10 radially inwards, thereby driving the spurs 32 through the outer insulating sleeve 46 and into the braided outer conductor shield 48. This completes an electrical connection between the outer conductor shield 48, the claw 10 and the conductor body 4.
It can be seen that connecting the plug 2 to a prepared coaxial cable 40 is very quick and simple, requiring only three operations: inserting the cable 40 into the plug 2, removing the spacer clip 14 and tightening the retaining cap 12. The electrical connection is reliable owing to the insertion of the spurs 32 into the braided outer conductor shield 48 and the engagement of the inner conductor 44 with the resilient tab 26 in the pin 8. Furthermore, a very strong mechanical connection is created between the plug 2 and the cable 40 owing to the fact that the spurs 32 are inserted through the outer insulating layer 46 and the braided outer conductor shield 48 into the dielectric insulator sleeve 50.
The second plug 102 as illustrated in Figures 3a-3c and 4a-4h is compatible with an F connector. The plug includes a three-part body member 104 comprising a front part 105, a rear part 106 and a connector piece 107, a support element 108, a claw 110 and a retaining cap 112. Optionally, the plug 102 may also include a removable spacer clip (not shown) similar to the clip 14 of the first plug 2 shown in figures 1a-1c and 2a-2d.
The front part 105 and the rear part 106 of the body member 104 are connected to each other by the connecting piece 107 so as to allow relative rotation of the front and rear parts about the central axis of the plug. The connecting part 107 may for example consist of a hollow cylindrical rivet having flanges at either end that hold the front and rear parts of the body member together.
The rear part 106 includes a locking formation in the form of a forwards-facing detent 115 that is engagable in a complementary locking formation comprising a rearwards facing notch 116 on the rear end of the front part 105. The connecting part 107 is dimensioned to allow a small amount of axial movement between the front and rear parts to allow engagement and disengagement of the complementary locking formations. When the locking formations are disengaged the front part 105 of the body member can be rotated relative to the rear part 106, allowing it to be attached to an F connector socket. When the locking formations are engaged, relative rotation of the front and rear parts 105, 106 is prevented, making it easier to screw the cap 112 onto the body member 104.
The front part 105 of the body member includes an internal screw thread 117 at its front end for engagement with a complementary screw thread of a conventional F connector socket, and an external nut 118 allowing the use of a spanner or wrench. The rear portion 106 of the body member includes an external screw thread 119. Internally, the rear part 106 of the body member has a large diameter bore 120 at its rear end and a smaller diameter bore 122 at its front end 16, providing a step 124 at the junction of the two bores.
The support element 108 comprises a generally cylindrical sleeve that is made of an electrically insulating material and has a diameter slightly smaller than the internal diameter of the connecting piece 107, so that it has an interference fit within the bore of the connecting piece 107. The support element includes a central bore that receives and supports the inner conductor 144 of the coaxial cable 140.
The claw 110 includes an annular disc 128 and four legs 130 that extend rearwards from the disc 128 approximately parallel to the longitudinal axis of the plug. Each of these legs 130 carries an inwards facing spur 132. The claw 110 is dimensioned to sit in the rear part of the large diameter bore 120 with the legs 130 protruding rearwards from the body member 104.
The retaining cap 112 comprises a hollow cylindrical sleeve having an internal screw thread that mates with the external thread 119 on the rear part 106 of the body member. At the rear end of the cap 112 a frusto-conical portion 134 provides an inwards inclined internal wall 136. This inclined wall 136 is configured to engage the ends of the legs 130 and to drive those legs inwards as the cap 112 is screwed onto the body member 104. The rear end of the cap includes an opening 138 to allow the insertion of a coaxial cable 140.
A process for attaching the plug 102 to a coaxial cable 140 will now be described with reference to Figures 4a-4h.
In Figures 4a and 4e the plug 102 is shown fully assembled and in a condition for receiving the prepared end of a coaxial cable 140. An end portion of the inner conductor 144 has been exposed by stripping away part of the outer insulator sleeve 146, the braided outer conductor shield 148 and the insulating dielectric sleeve 150.
In Figures 4b and 4f the prepared end of the coaxial cable 140 has been inserted fully into the plug 102, so that the cut ends of the outer insulating sleeve 146, the braided conductor shield 148 and the dielectric sleeve 150 abut the annular disc 128 of the claw 110. The solid central conductor 144 has been inserted through the insulating support element 108. The locking formations 115, 116 are disengaged, allowing the front part 105 of the body member 104 to rotate relative to the rear part 106.
In Figures 4c and 4g the locking formations 115, 116 are engaged, preventing the front part 105 of the body member 104 from rotating relative to the rear part 106 and thus allowing the retaining cap 112 to be tightened.
Figures 4d and 4h illustrate the final stage of the attachment process, in which the retaining cap 112 has been tightened onto the body member 104. As the cap 112 is tightened the inclined walls 136 of the frusto-conical portion 134 push the legs 130 of the claw 110 radially inwards, thereby driving the spurs 132 through the outer insulating sleeve 146 and into the braided outer conductor shield 148. This completes an electrical connection between the outer conductor shield 148, the claw 110 and the conductor body 104.
As with the first embodiment of the invention, connecting the plug 102 to a prepared coaxial cable 140 is very quick and simple, consisting only of inserting the cable 140 into the plug 102 and tightening the retaining cap 112. The electrical connection is reliable owing to the insertion of the spurs 132 into the braided outer conductor shield 48. Furthermore, a very strong mechanical connection is created between the plug 102 and the cable 140 owing to the fact that the spurs 132 are inserted through the outer insulating layer 146 and the braided outer conductor shield 148 into the dielectric insulator sleeve 150.
Figures 5 and 6a to 6f show a cable trimming tool 200 for use when attaching either of the plugs to a coaxial cable. The tool 200 may be supplied separately as a kit with one or more plugs 2, 102.
The cable trimming tool 200 includes a body 202, a cutter 204 and two helical springs 206. The body 202 is a moulded plastic component comprising a plate 208 with a peripheral strengthening rib 210. The plate 208 is approximately circular in shape having upper and lower arcuate cut- outs 212, 214 in the top and bottom edges. A central portion of the plate 208 is double-walled providing a slot 216 that extends into the body 202 from the upper cut-out 212, for receiving the cutter 204. The body 202 includes a circular hole 218 that extends through the centre of the plate 208 perpendicular to the plane thereof. A measuring mark 220 is provided on the face of the plate 208 above the hole 218.
The cutter 204 comprises a moulded plastic frame 222 that supports a metal blade 224. The frame 222 includes a lower portion 226 that fits into the slot 216 in the body 202 and an upper rib 228 that can be seated against the edge of the upper cut-out 212. Two legs 230 are provided at opposite ends of the frame, each leg including an outward facing detent 232 that engages a corresponding recess within the slot 216 to secure the cutter 204 to the body 202. The springs 206 are compressed between the cutter 204 and the body 202 and serve to bias the cutter upwards.
The cutter 204 can slide up and down within the slot 216 between upper and lower positions. The springs 206 are compressed between the cutter 204 and the body 202 and serve to bias the cutter upwards towards the upper position. The cutter 204 can be pressed downwards to the lower position by squeezing the upper rib 228 and the lower arcuate portion 214 between thumb and forefinger. When the cutter is in the lower position the blade 224 extends a predetermined distance across the hole 218, this distance being chosen so that when a coaxial cable 140 of a chosen size is inserted into the hole 218, the blade cuts through the outer insulating sleeve 146, the braided outer conductor shield 148 and the dielectric insulator sleeve 150 without cutting the central conductor 144. When the cutter 204 is released it returns to the upper position in which the blade 224 is clear of the hole 218, allowing a coaxial cable to be inserted into or removed from the hole.
Use of the cable trimming tool 200 is illustrated in Figs. 6a to 6e. First, the end of a coaxial cable 140 is placed level with the measuring mark 220 and the cable is grasped at the point P where it crosses the lower arcuate cut-out 214 (Fig. 6a). Then, the end of the cable is inserted into the hole 218 (Figs. 6b, 6c) so that the point P is level with the face of the body 202. This ensures that the correct length of insulator etc is stripped from the end of the cable. The cutter 204 is then pressed downwards (Fig. 6d) and the trimming tool 200 is rotated around the cable 140 to produce a circumferential cut all around the cable 140. Finally, the cable 140 is withdrawn from the tool 200 (Fig. 6e) and the cut portion of the outer insulator sleeve, the braided shield and the dielectric insulator layer is removed to leave an exposed length of the inner conductor 144.
Various modifications of the invention are of course possible. For example, the F connector plug may be designed for a push fit with an F connector socket instead of a threaded screw fit. In that case, the three-part body may be replaced by a simple one-part body.

Claims

A connector plug (2, 102) for use with a coaxial cable (40, 140) comprising inner and outer conductors (44, 144, 48, 148), an inner insulator (50) between the inner and outer conductors and an outer insulator sleeve (46, 146), the connector plug (2, 102) comprising
a body member (4, 104) having a connector portion (16, 105) at a front end for connection to a coaxial socket and an externally threaded portion (18, 119) at a rear end, said body member configured for electrical connection to the outer conductor (48, 148),
a support element (6, 108) configured to receive and support the inner conductor,
a gripper element for gripping the cable, the gripper element comprises a claw (10, 110) having a plurality of radially adjustable legs (30, 130), at least one of the legs including a piercing element (32, 132) that is configured to pierce the outer insulator sleeve and establish an electrical connection between the body member (4, 104) and the outer conductor (48,148) when the gripper element is in a gripping configuration, and
a retaining cap (12, 112) having an internal screw thread (117) that mates with the external screw thread (119) on the rear part (106) of the body member and a frusto-conical portion (34, 134) that provides an inwards inclined internal wall (36, 136),
wherein the retaining cap (12, 112) is configured to adjust the gripper element between a gripping configuration and a non-gripping configuration by adjusting the radial positions of the legs (30, 130),
wherein the retaining cap (12, 112) is adjustable by being screwed onto the body member between first and second axially displaced positions,
wherein when the retaining cap is in the first position the gripping element is disposed in the non-gripping configuration, and when the retaining cap is in the second position the gripping element is disposed in the gripping configuration;
characterised in that
the body member (4, 104) has a first bore (20, 122) at the front end and a larger second bore (22, 120) at the rear end providing a step (24, 124) at a junction of the two bores,
the gripping element is dimensioned to sit in a rear part of the second bore with the legs protruding rearwards from the body member, and
the connector plug (2, 102) includes a spacer element (14) that is removably attached to the body member, said spacer element being configured such that when attached to the body member it prevents movement of the retaining cap (12, 112) from said first position to said second position.
A connector plug according to claim 1, wherein the support element (6) includes a connector pin (8) that is configured to receive and support the inner conductor (44, 144).
A connector plug according to claim 2, wherein the connector pin (8) includes a resilient connector element (26) that establishes an electrical connection with the inner conductor (44, 144).
A connector plug according to claim 1, wherein the support element (108) is configured to support the inner conductor (44, 144) so that it serves as a connector pin.
A connector plug according to any one of the preceding claims, wherein the body member (104) includes a front part (105) and a rear part (106) that are connected together for relative rotation wherein the front part (105) includes the internal screw thread (117) for engagement with the coaxial socket and the rear part (106) has the externally threaded portion (119).
A connector plug according to claim 5, wherein the front and rear parts (105, 106) of the body member include complementary locking formations (115,116) that may be engaged by relative axial movement of the front and rear parts of the body member to prevent relative rotation.
A connector plug according to claim 6, wherein the complementary locking formations may be disengaged by relative axial movement of the front and rear parts of the body member to allow relative rotation by relative axial movement of the front and rear parts of the body member.
A plug kit comprising
at least one connector plug (2, 102) according to any one of claims 1 to 7 and
a coaxial cable trimming tool (200), the coaxial cable trimming tool including a body member (202) with an aperture (218) for receiving a coaxial cable, and a cutter element (204) including a blade (224) that can be adjusted relative to the aperture between cutting and non-cutting positions,
wherein when the blade is in the cutting position it extends across the aperture to cut a coaxial cable located in the aperture substantially to the depth of the inner conductor.
A plug kit according to claim 8, wherein the cutter element is resiliently biased to the non-cutting position.
A method of fitting the connector plug (2, 102) of any one of claims 1 to 7 to a coaxial cable that comprises inner and outer conductors (44, 144, 48, 148), an inner insulator (50) between the inner and outer conductors (44, 144, 48, 148)and an outer insulator sleeve (46, 146), the method including:
providing the connector plug (2, 102) fully assembled and in a condition for receiving a prepared end of a coaxial cable (40, 140),

trimming the coaxial cable to expose the inner conductor (44, 144),

inserting the trimmed cable into the assembled connector plug (2, 102), removing the spacer element (14), and

tightening the retaining cap (12, 112) to establish an electrical connection between the body member and the outer conductor by piercing the outer insulator layer (46, 146) with the piercing element (32, 132).